Australian patents 609089 and 655076, which correspond to U.S. Pat. Nos. 4,886,563 and 5,674,349 respectively, disclose machinery for forming a corrugated paperboard structure having flute tip to flute tip bonding in which two sets of corrugating rolls are aligned so that two corrugated mediums are brought into tip to tip registration in the gap between the central two rolls and the combined mediums are then conveyed by an adjacent carrier roll to further downstream processing.
Patent 655076 identified that lack of rigidity in the support frame and in the corrugating rolls can lead to relative movement between the corrugating rolls and consequently to misalignment of the flute tips along the length of a roll, that is transversely of the paperboard. It attempted to alleviate the problem using end gears to control the relative position of the flute tips along the length of the two rolls. Misalignment of the flute tips in the finished board has a deleterious effect on the strength properties of the board.